While
an Anglo-Norman castle was built at the site of Belfast in the 12th Century,
it was not until the plantation of Ireland by English and Scots settlers
in the 17th Century, that Belfast began to grow. At that time Belfast
was a Protestant city as the planters excluded the native
Catholic population. It was not until the early 1800s, as the city industrialised,
that large numbers of Catholics became attracted to Belfast for work.
By the 1850s, Catholics made up one third of the population of the city.
The proportion of Catholics and Protestants changed from time to time
since then: at present in the core city (i.e. excluding the
suburbs which have been swallowed up with urbanisation) Catholics make
up almost half of the population.

These
populations are, as we have seen, very segregated. The levels of segregation
seem to vary over time. In the mid 19th Century about 50% of the population
was estimated to live in segregated streets  about 50% lived in
mixed streets. During times of inter-ethnic tension segregation levels
rise. This may be due to intimidation of people out of their homes or
voluntary relocation into areas perceived as safer. During periods of
reduced inter-communal tensions it might be thought that many people would
return to their original homes. However this does not appear to happen.
Professor Tony Hepburn has called this the segregation ratchet.
In the 1960s, for example, 67% of Belfasts core city residents lived
in segregated streets. By the 1970s this had risen to 77% and to 78% by
the 1980s. It will be interesting to see whether an outcome of the peace
process will lead to more mixed residential areas. Ongoing conflict at
ethnic interfaces in Belfast would suggest that this is unlikely, as the
ratchet slips up another notch.